Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$100.68	12.640%	$113.406	$113.41	$113.40	$113.40
Purchase #2	$100.82	4.685%	$105.5434	$105.54	$105.55	$105.50
Purchase #3	$242.35	4.236%	$252.6159	$252.62	$252.60	$252.60
Purchase #4	$171.36	12.238%	$192.331	$192.33	$192.35	$192.30
Purchase #5	$138.86	5.690%	$146.7611	$146.76	$146.75	$146.80
Purchase #6	$103.56	12.577%	$116.5847	$116.58	$116.60	$116.60
Purchase #7	$152.59	3.611%	$158.1	$158.10	$158.10	$158.10
7 purchase totals =	$1,010.22		$1,085.3421	$1,085.34	$1,085.35	$1,085.30